This invention relates to liquid crystal display (LCD) devices and means for receiving data from a human operator, such as keyboards, and more particularly to a liquid crystal display device which may be used for receiving information from a human operator as well as displaying information.
LCD's are very well known in the art and are frequently used as display devices for displaying information outputted from a calculator, a watch, appliances, or other electronic apparatus. The LCD devices have undergone considerable improvement in the last several years and are presently used in many applications; LCD's are particularly well suited for use with portable, battery-powered electronic apparatuses, such as calculators and watches, because LCD's require very little power to display information in these battery-powered apparatuses. It should be appreciated, however, that the instant invention may be used, if desired, in any application using LCD's to display information.
The electronic appliances and apparatuses which utilize LCD's often frequently include a keyboard, that is, an array of key switches or push buttons, or other types of electrical switches and contacts to input information to the appliance or apparatus. In the embodiment of a calculator, for example, the keyboard may include ten numeral keys, a decimal point key, and five or more function keys (plus, minus, multiply, divide and equals). Further, those familiar with the calculator art will realize that as the complexity of the calculator increases, the number of functions which the calculator may accomplish likewise increases. Of course, given the small size of these hand-held calculators and the size of the human finger, there is a practical limit on the number of keys which may be provided on a calculator or other such electronic device to access the functions which it may perform. Of course, other small appliances may benefit from having additional keys. Additionally, having the capability to program the functions which the keys perform can greatly increase the flexibility of the calculator or other appliances.
It was therefore, one object of this invention that a combination display device and keyboard device be provided for an electronic calculator or other electronic apparatus. It was another object of this invention that a liquid crystal display device be adapted for receiving inputs from a human operator in addition to displaying information to the human operator. It was yet another object that the number of keys presented to the operator be selectable. It was still yet another object that the legends associated with the keys be selectable.
The foregoing objects are achieved as is now described. A LCD device having a rear substrate, a transparent front plate, a plurality of segments formed on the substrate and on the plate, and a liquid crystal material disposed between the substrate and plate is provided with a plate which will deflect toward the substrate in response to the application of pressure by a human operator. The segments of the LCD device are actuated by conventional means to output information to the operator. This information will include selected segments which are actuated to define one or more regions on the device where the operator may depress the front plate to input information to the apparatus to which the LCD is coupled. The segments in these one or more regions are sensed for a change in capacitance between the segments mounted upon the substrate and the segments mounted upon the front plate within these regions. The change in capacitance occurs when the operator depresses the cover thereby increasing the capacitance imposed by the liquid crystal material between opposing segments. By appropriating energizing and sensing the segments of the LCD device, the number of regions (that is, the number of keys) is selectable as are the legends displayed in conjunction with these regions.